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Alternative namesSpinal tap; Ventricular puncture; Lumbar puncture; Cisternal puncture; Spinal fluid specimen
DefinitionCSF collection is a procedure to obtain a specimen of cerebrospinal fluid (CSF). CSF is the fluid that bathes, cushions, and protects the brain and spinal cord. It flows through the skull and spine in the subarachnoid space, which is the area inside the arachnoid membrane.
How the test is performed
Lumbar puncture (spinal tap) is the most common means of collecting a specimen of CSF. You are positioned on your side with your knees curled up to your abdomen and your chin tucked in to your chest. (Occasionally this procedure is performed with the person sitting bent forward).
The skin is scrubbed, and a local anesthetic is injected over the lower spine. The spinal needle is inserted, usually between the 3rd and 4th lumbar vertebrae.
Once the needle is properly positioned in the subarachnoid space, pressures can be measured and fluid can be collected for testing. After the sample is collected, the needle is removed, the area is cleaned, and a bandage is applied. You will be asked to remain flat, or nearly flat, for 6 to 8 hours after the test.
Lumbar puncture (with fluid collection) may also be part of other procedures, particularly a myelogram (X-ray or CT scan after dye has been inserted into the CSF).
Cisternal puncture involves insertion of a needle below the occipital bone (back of the skull). It can be hazardous because the needle is inserted close to the brain stem.
Ventricular puncture is even more rare, but may be indicated when sampling of CSF is necessary in people with possible impending brain herniation . It is usually performed in the operating room. A hole is drilled in the skull and a needle is inserted directly into the lateral ventricle of the brain.
How to prepare for the testYou must sign a consent form. You must be prepared to remain in the hospital for at least 6 to 8 hours, and you must remain flat.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel
The position may be uncomfortable, but it is imperative that you remain in the curled position to avoid moving the needle and possibly injuring the spinal cord.
Overall, discomfort is minimal to moderate. The entire procedure usually takes about 30 minutes, but it may take longer. The actual pressure measurements and fluid collection only takes a few minutes.
Why the test is performedThis test is performed to measure pressures within the cerebrospinal fluid and to collect CSF for testing. CSF collection can be a diagnostic test for many neurologic disorders, particularly infections and brain/spinal cord damage.
Note: mg/ml = milligrams per milliliter; mEq/L = milliequivalent per liter
What abnormal results mean
Additional conditions under which the test may be performed:
What the risks are
Special considerationsThis test should not be performed on people in which increased intracranial pressure is suspected.
Update Date: 5/8/2003Elaine T. Kiriakopoulos, M.D., M.Sc., Department of Neurology, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT